DNA Scission After Focal Brain Ischemia

Abstract

Background and Purpose Species- and model-dependent differences in cell response to focal brain ischemia may underlie differences in adhesion receptor expression. The aim of this study was to quantitatively evaluate the spatial and temporal distribution of dUTP incorporation into damaged DNA, as an indicator of ischemic injury, in the corpus striatum. Methods Cerebral ischemia was produced in 16 nonhuman primates and 19 rats by occluding the middle cerebral artery (MCA:O) with reperfusion for various periods. In situ dUTP was incorporated into cells with DNA damage by terminal deoxynucleotidyl transferase (TdT), DNA polymerase I, or the Klenow fragment of DNA polymerase. Dual immunolabeling experiments with immunoprobes against neuronal, vascular, or glial marker proteins were performed. Results Significant topographical differences in dUTP between the two species were seen. In both models the TdT and polymerase I regions changed characteristically during focal ischemia. The number and density of dUTP-labeled cells increased with time from MCA:O and were dramatically different between the species (2 P <.001). By 2 hours of ischemia, the density of dUTP label was 48.8±10.3 cells/mm ² in the primate and 2.4±0.8 cells/mm ² in the rat (2 P <.05), but these values became nearly identical by 24 hours of reperfusion. In the primate, 80.0±6.6% of labeled cells displayed microtubule-associated protein-2 antigen (at 2-hour MCA:O), while 1.8±0.5% were associated with microvessels at 24 hours of reperfusion. Conclusions In situ detection of DNA damage, accomplished by three methods, reveals distinct temporal, topographical, and density differences in ischemic injury to cells in the primate and the rat corpus striatum as a result of MCA:O.